Runs

A run is one sanderling test invocation: launch the app, explore it under the spec for a fixed duration, write a trace. Runs typically last minutes to hours, not seconds.

A run is not a unit test. The closer picture is: boot a fuzzer for an hour and see what breaks. A violated property is recorded in the trace and exploration continues, so one run can surface many bugs.

Lifecycle

sanderling test --spec spec.ts --bundle-id com.example.app --duration 30m
  │
  ├── launch the app under test (pass --clear-data to wipe app data first)
  ├── boot the sidecar (or connect to Chrome on web)
  ├── bundle the spec, load it into the JS runtime
  │
  ├── step 0..N:  read state, check properties, pick and perform an action
  │
  └── stop when --duration elapses (or on Ctrl+C)
        └── trace written to ./runs/<timestamp>/
              ├── trace.jsonl
              ├── screenshots/
              └── meta.json

The trace is written incrementally. An interrupted run is complete up to the step where it stopped.

App state across runs

By default each run wipes app data before launch and starts cold. Pass --clear-data=false to resume whatever the previous run left behind (an account, cached responses, completed onboarding). See the CLI reference.

Why runs are long

sanderling does not restart the app every few steps. Restarting throws away two things.

Accumulated data. Accounts created, items added, caches warmed, settings changed. Interesting bugs live in apps with history, and a restart wipes it.

Deep app states. Many bugs live in states that take many actions to reach: nested settings, a loaded cart, the screen after the third transaction. A 50-step path to "cart with 3 items" never happens if every run starts cold.

Long runs reach states that restart-per-test approaches structurally cannot.

Setup cost is paid once

Preconditions like login run through the spec's setup export (see the case study). They fire when their condition is unmet and go quiet after, so login costs a few seconds once per run, not once per test case.

Session state

Session tokens, keychain entries, shared preferences, and cookies survive the whole run. If the app logs the user out mid-run, the gating extractor flips, setup re-engages, and the run logs back in. No retry logic needed in the spec.

Termination

A run ends when:

• --duration elapses, or
• the process is interrupted (Ctrl+C).

Additional conditions (--max-steps, --exit-on-violation, hard crash handling) land in the v0.1.0 milestone.